How to reinstall old iOS software?

I have an older iPod touch which which supports up to iOS 6.1.6 and nothing newer. This device is equipped with a Linea Pro barcode scanner and previously had an application called "Web Barcode" installed. Recently I was attempting to do some work on a web application I wrote and realized that I needed to update to a newer version of Web Barcode - but unfortunately the Apple ID saved on my device was deactivated a few years ago. So I went to settings and updated it with my current Apple ID. Then again tried to update the App from the Apple store. Still no dice - it was asking me for the password on the old account.

So then I figured I'd just remove it and reinstall from scratch. Deleted the app and went to the store but now I am met with a message that the new version requires at least iOS 8.0.

I feel I followed a very logical series of steps to update this application and while I can understand that I won't be able to install the newest version, how can I get the old version back? The device is completely useless without the barcode scanning application and the Apple store is now refusing to install any version at all on my device.

What can I do to get the original version of this application reinstalled?

Solution 1:

To download the last compatible version of an app, the app must be in your purchase history for that Apple ID already. Use iTunes 12.6.3 to download the app, signing in with your new Apple ID. Once the app is in your purchase history, attempting to download it again on your device should prompt you to accept an older version of the app.